This invention relates generally to electronic systems, e.g., communications, radar, etc., which employ a plurality of radio frequency (RF) power transistors and more particularly to a method and apparatus for enhancing system performance and reliability by controlling the operating temperature of each transistor.
It is well known that the overall performance (including longevity and/or reliability) of electronic systems can be adversely affected if component operating temperatures are permitted to rise above certain rated values. Thus, systems utilizing large transistor arrays frequently incorporate cooling subsystems which monitor array operating temperatures and act to cool the array by, for example, increasing coolant flow rate. Although such cooling subsystems typically enhance system performance, they generally fail to rapidly respond to localized temperature excursions of individual transistors which can produce xe2x80x9chot spotsxe2x80x9d and lead to thermal runaway with potentially catastrophic failure. Thus, the functionality of an entire transistor array can be significantly compromised as a consequence of a single transistor experiencing an excessive junction temperature excursion.
The present invention is directed to a method and apparatus for use with a transistor array for enhancing the array""s performance and/or reliability and/or longevity by sensing the temperature of each transistor in the array and initiating corrective action to maintain its temperature within a desired operating range.
In accordance with the invention, each of a plurality of array transistors has a temperature sensor closely thermally coupled thereto, preferably mounted within the transistor package, in close physical proximity to the transistor junction.
In a preferred embodiment, each temperature sensor is configured to supply digital output signals representing the junction temperature of a single transistor. The output signals are supplied to a digital controller which is connected in a feedback loop to control one or more parameters affecting the temperature producing behavior of each transistor. More particularly, a controllable temperature modifying device is coupled to each transistor and is controlled by the digital controller to maintain junction temperature within a specified range. Each such temperature modifying device can control one or more parameters; e.g., the magnitude of the drive current and/or supply voltage applied to the transistor and/or the flow rate of coolant provided to the transistor.